Travelling grate stokers



Oct. 25, 1966 A. s. PEACOCK 3,

TRAVELLING GRATE STOKERS Filed Aug. 13, 1964 6 Sheets-Sheet l Oct. 25, 1966 A. s. PEACOCK 3,280,768

TRAVELLING GRATE STOKERS Filed Aug. 15, 1964 6 Sheets-Sheet 2 Oct. 25, 1966 A. s. PEACOCK 3,280,768

TRAVELLING GRATE STOKERS Filed Aug. 13, 1964 6 Sheets-Sheet 5 25, 1966 A. s. PEACOCK TRAVELLING GRATE STOKERS 6 Sheets-Sheet 4 Filed Aug. 13, 1964 Oct. 25, 1966 A. s. PEAcocK TRAVELLING GRATE STOKERS 6 Sheets-Sheet 5 Filed Aug. 15, 1964 1 E llll|llll|liiilli lllllllllll lkmfir Fm? !i||:|i!i! u U U F D u IIHIIIIMHHNIIIIIIA'IHIIN UlllllYl fillHHlilIlU Q R Q Oct. 25, 1966 A. s. PEACOCK 3,280,768

TRAVELLING GRATE STOKERS Filed Aug. 1:5, 1964 6 Shets-Sheet e United States Patent 3,280,768 TRAVELLING GRATE STOKERS Arthur Sidney Peacock, The Mount, 41 Uphill Road, Mill Hill, London, England Filed Aug. 13, 1964, Ser. No. 389,264 18 Claims. (Cl. 110-40) This invention relates to travelling grate stokers.

According to the present invention there is provided a travelling grate stoker comprising a pair of endless chains disposed side by side in spaced relationship, a series of ash pans extending between and carried by the chains and adapted to collect ash falling through superjacent parts of the upper run of the grate and to carry collected ash and to discharge the ash at the rear of the stoker, grate sections carried by respective pans and each formed of bars arranged with combustion air spaces therebetween and extending transversely of the direction of movement of the grate, and a continuous guide track for each chain which serves to support the chain and constrain it to move in a predetermined path.

Further, according to the present invention there is provided a travelling grate stoker grate section carrier in the form of an ash pan having a rear wall, a bottom parallel or substantially parallel with the fuel supporting surface of the grate section, an ash-retaining ledge at the front of the ash pan, a front transom spaced from the ledge, adapted together with the rear wall to locate a set of grate bars extending transversely of the pan, walls closing the edges of the pan and means for coupling the pan at its ends to respective chains.

The invention will now be described, by way of example, with reference to the accompanying drawings in which:

FIGURE 1 is a sectional side elevation of a travelling grate stoker;

FIGURE 2 is a plan of the stoker frame, the grate being absent;

FIGURE 3 is an elevation of the stoker in section on the line IIIIII of FIGURE 1;

FIGURE 4 is a plan of an ash pan;

FIGURE 5 is an elevation of the ash pan in section on the line V-V of FIGURE 4;

FIGURE 6 is a plan of a grate section adapted to be carried by the ash pan;

FIGURE 7 is an isometric view of part of the length of a chain adapted for use in the travelling grate stoker; and

FIGURE 8 is an isometric view of part of the stoker, with many parts removed, showing pictorially the manner of mounting the ash pans on the chain links and the arrangement of grate bars of grate sections carried on ash pans.

Referring to FIGURES l to 3 of the drawings, a travelling grate stoker I is arranged for rearward movement in the upper run of the grate 2 to carry a bed of coal into the furnace from a suitable coal supply hopper 3 at the front of the grate and to discharge ash over ash bars 4 at the rear of the grate into a subjacent water-sealed ash hopper 5. The stoker comprises four stoker sections 1A, 1B, 1C and 1D arranged side by side and each stoker section comprises a pair of endless chains 6, one chain at each side of the stoker section, carrying a series of ash pans 7 which support respective sections 8 of the grate 2.

The nature and construction of the chains, ash pans and grate sections will be described in detail with reference to FIGURES 4 to 8. Each chain is provided at its outer side with rollers 9 and by means of the rollers on the chains the upper run of the grate and the lower run of the grate are supported by horizontal longitudinally extending upper and lower I-section members 10 of the stoker frame; the lower flanges 12 of the I-section members 10 serve as roller tracks and the rollers 9 are of outwardly tapering form according to the angle of the flange surface. At the front of the stoker the front ends of corresponding upper and lower I-section members 10' are joined by semi-circular or substantially semi-circular lengths 13 of I-section and at the rear of the stoker the rear ends of corresponding upper and lower I-section members 10 are joined by semi-circular lengths 14 of I-section.

Each chain is provided at its inner side with bosses 15 for engagement by the teeth 21 of a driving sprocket wheel 22 which is disposed at the rear end of the stoker above the hopper 5. The sprocket wheels 22 are mounted on a common driving shaft 23 driven by a motor (not shown).

Referring to FIGURES 4 to 8, each ash pan 7 includes a flat bottom 24, a front prolongation of the bottom curved first upwardly then downwardly to form an upwardly convex front retaining ledge 25 terminating in a front lip 26, a rear retaining wall 27 rising from the bottom 24 near the rear end thereof, retaining end walls 28 near the respective ends 24 of the ash pan and an intermediate wall 29 similar and parallel to the end walls 28 and halfway therebetween.

The ash pans of each adjacent pair of ash pans are so close to one another in the upper run of the grate that the rear end 30 of the bottom of the front ash pan is to the rear of the front lip 26 0f the rear ash pan; the rear retaining wall 27 rising from the bottom of the front ash pan, before terminating in a vertical uppermost portion 31, curving forwardly then rearwardly so as to allow adequate space between the said wall and the front lip 26 of the rear ash pan for combustion air to flow upwardly between the ash pans.

The end walls 28 and the intermediate wall 29 have horizontal upper edges 32 which afford grate bar support surfaces; the said walls terminate rearwardly in the rear wall 27 and forwardly in respective supports 33 which rise with a slight forward inclination from the lip 26 and carry a front transom 34 which is adapted to act as a grate bar. The upper part of the transom has a forwardly inclined front surface 35 adapted to over-hang the vertical uppermost portion 31 of the rear retaining wall 27 of an adjacent ash pan. The lower edge of the transom is spaced from the ledge 25 so that air flowing upwardly between the ash pan and the adjacent preceding ash pan may flow rearwardly into the ash pan.

Each grate section 8 carried by an ash pan 7 is formed as a unit comprising fourteen grate bars 41 which are held in their assembled positions by a pair of rods 42 at respective ends of the unit which are welded to the ends of the grate bars, the grate bars being spaced so that combustion air may flow upwardly in the gaps between the bars. The grate bars are of rectangular cross-section and are cut from strip; they have all the same width and the same length, but the first, third, fifth, seventh and thirteenth grates bars from the front have a common depth which is less than the depth of the remaining grate bars which have the same depth as that of the transom 34 and are supported on the upper edges 32 of the end and intermediate walls 28 and 29. The upper surfaces of the grate bars, when the grate section is carried by its ash pan in the upper run of the grate, lies in a horizontal plane in which the upper surface of the transom34 also lies.

The grate section is positioned between the transom 34 at the front of the ash pan and the uppermost portion 31 of the rear wall 27 of the ash pan by couplings of the projection and socket type. Thus the rear face of the transom 34 is formed with two spaced recesses 43 respectively complementary to projections 44 provided on the front face of the front grate bar of the grate section and the front face of the uppermost rear wall portion 31 is formed with three spaced projections 45 adapted to extend within complementary recesses 46 formed in the rear grate bar of the section. The projections 44 extend forwardly from the front grate bar sufliciently to ensure a spacing between the transom 34 and the front grate bar for the appropriate upward flow of combustion air therebetween and the depth of the recesses 46 in the rear grate bar is limited to ensure a spacing between the rear grate bar and the rear wall upper portion 31 for the appropriate upward flow of combustion air therebetween.

The grate section possesses resilience between its front and rear bars that enables it to be readily disengaged from the ash pan. Thus by simply inserting an implement, which may be nothing more than a rod or bar with tapered end, between the front grate bar and the transom 34 and operating the implement to flex the said grate bar in a rearward direction the projections 44 thereon may be released from the recesses 43 in the transom 34, whereupon the front end of the grate section may be moved away from the ash pan and then forwardly until the projections 45 on the uppermost rear wall portion 31 release the rear grate bar. By an equally simple and reverse operation a new grate section may be engaged relatively to the ash pan.

At each end of the ash pan a supporting lug 47 projects horizontally and laterally of the grate from the ash pan bottom 24. The lug is adapted to fit in a recess 48 in an adjacent link 49 of the chain 6 and is locked in the recess by a key 50 held in position through engagement with the eighth to twelfth grate bars from the front of the disengageable grate section.

The lug 4'7 fits in the bottom of the recess 48 and the head 51 of the key 50 fits in the recess above the lug. The key head 51 is a flat body with rounded front and rear ends 52 which fit in corresponding front and rear concave grooves 53 in the recess. The key shank 54 is in the form of a flat plate which extends transversely of the key head 51 and transversely of the grate bars 41 of the grate section carried by the ash pan and its end is adjacent a shoulder 55 formed in the eighth to twelfth grate bars so that so long as the grate section 8 associated with the ash pan is in position the key 50 is unable to move from the locking position.

Each chain 6 is formed of inner links 49A alternating with outer links 49B and each inner link 49A is formed centrally adjacent its outer edge with a projection 61 extending outwardly with respect to the corresponding stoker section, into which projection 61 the recess 48 extends and each outer chain link 49B is formed centrally adjacent its inner edge with a projection 62 extending inwardly with respect to the corresponding stoker section and penetrated by the recess 48.

Each inner link 49A of each chain 6 is formed at its inner face with a circular driving boss for engagement by the teeth 21 of a driving sprocket wheel 22. The links 49A, 49B of each chain are hinged together by means of bushes 63 in which spindles 64 for the rollers 9 are rotatably carried and the roller spindles 64 passing through the bushes 63 extend co-axially through the chain driving bosses 15 at the inner faces of the inner links 49A. At their inner ends the spindles 64 are fitted with washers 65 and split pins 66 to maintain the spindles in position and at their outer ends adjacent the rollers 9 the spindles are formed with parts 67 of increased diameter for engaging the outer ends of the bushes 63.

As previously explained, the rollers 9 of each chain are arranged to roll on a lower flange 12 of an I-section member 10. The links 49A, 49B of each chain at their outer faces are formed at the edges which are upper edges in the upper run of the grate with longitudinal ribs 68 arranged, in the upper arm of the grate, to overlap the upper flange 69 of the I-section member 10; the said upper flange is fitted with a plate 70 an edge 71 of which is opposed to the extremities of the ribs 68. In this way an air seal is formed.

Reverting to FIGURES 1 to 3, the stoker frame, which includes the upper and lower longitudinally extending I-section members 10, includes transverse frame members 72 and also includes vertical transverse plates 73 associated with some of the transverse frame members which form ends of a windbox 74 provided between the upper and lower runs of the grate and which divide the wind box into four compartments 81, 82, 83 and 84 extending from one side of the stoker to the other and having separate dampers 85 for the control of combustion airadmission thereto from a lateral windbox 86 to one side of the stoker.

Above those of the transverse plates 73 that divide the windbox 74 are transversely extending sealing plates 87 adapted to minimize air leakage from one windbox compantment to another; the upper surface of each sealing plate is contiguous with the bottom 24 of an ash pan or the bottoms of ash pans, the arrangement being such that before the rear portion of the bottom of one ash pan has passed from above the plate 87 the front portion of the next sucessive ash pan has moved above the plate. Suitable dead plates 88 are provided at the ends of the upper run of the grate.

The grate bars 41 have such lengths that adjacent ends of the grate bars of adjacent stoker sections 1A, 1B, lC and 1D nearly abut one another; the outer ends of the grate bars of the two outer stoker sections )lA and ID are adjacent the refractory 89 at the base of the furnace side walls 90. The transom 34 of each ash pa-n has the same length as the bars 41 of the grate section carried by the ash pan, while the upper rear wall portion 31 of the ash pan is formed with extensions 91 that bring the total length thereof to that of the corresponding grate bars.

In the operation of the stoker, combustion air at appropriate pressure cont-rolled by the dampers 85 is supplied to each compartment of the windbox 74 and the air flows from the windbox upwardly between the ash pans and between the transom-s 34 and the ledges 25 of the ash pans into the spaces below the grate bars 41, whence the air flows upwardly into the superjacent fuel bed through the air gaps between the grate bars comprising the grate bars 41 and the transoms 34. In practice, the grate described is capable of operating with relatively high combustion rates with relatively low carbon loss in the ash and with relatively low metal temperatures of the grate bars. The tractive effort for driving the chains is relatively low.

Riddlings falling through the air gaps of the grate collect in the subjacent ash pans and are carried thereby to the rear of the grate and discharged from the ash pans. In the discharge of riddlings, the riddlings fall from each ash pan, as it is progressively tilted during the rotation of the driving sprocket wheels 22, over the ledge 25 of the ash pan onto the concave rear surface of the rear wall 27 of the preceding ash pan and then from the said surface into the hopper as the preceding ash pan becomes completely inverted. It will be appreciated that since the riddlings are removed and discharged into the hopper the necessity for frequent removal of riddlings from the windbox compartments, and the necessity for designing the windbox compartments to facilitate frequent riddlings removal therefrom, are avoided. Moreover, the riddlings richer in carbon from earlier parts of the fuel bed, the separate accumulation of which might lead to fires, are mingled with or overlaid in the ash pans by riddlings less rich in carbon or of ash from later par-ts of the fuel bed.

In the upper run of the grate the upper flanges 69 of the I-beams and the longitudinal ribs 68 of the chain links which ribs overlap the said flanges protect the rollers 9 from downward heat radiation from the fuel bed and grate bars.

After removing a grate section 8 from an ash pan 7 the corresponding keys 50 may be withdrawn from the recesses 48 in the corresponding chain links 49 and then the ash pan may be withdrawn. Fit-ting of a fresh ash pan may be effected in an equally simple and reverse manner.

It will be appreciated that great flexibility in design may be attained by the provision of several standard lengths of ash pans, grate bars and transverse frame elements which may be combined in plural section stokers to give units of different total grate widths. By the provision of standard side firame elements of different lengths even greater flexibility may be achieved. The drawings refer to a four-section stoker in which the stoker section 1B has a smaller standard width than the sections 1A, 1C and 1D.

What I claim as my invention and desire to secure by Letters Patent is:

1. A travelling grate stoker comprising a pair of endless chains disposed side-by-side in spaced relationship, a series of ash pans extending between and carried by the chains and adapted to collect ash falling through superjacent parts of the upper run of the grate and to carry the collected ash and to discharge the ash at the rear of the stoker, grate sections carried by respective pans and each formed of bars arranged with combustion air spaces therebetween and extending transversely of the direction of movement of the grate, a continuous guide track for each chain which serves to support the chain and constrain it to move in a predetermined path, means longitudinally sectionalizing the air space below the upper run of the grate into compartments, and means for separately controlling the air pressures in different compartments, said ash pans in the upper run of the grate providing sealing surfaces cooperating with complementary means in limiting leakage between adjacent air compartments.

2. A travelling grate stoker comprising a pair of endless chains disposed side-by-side in spaced relationship, a series of ash pans extending between and carried by the chains and adapted to collect ash falling through superjacent parts of the upper run of the grate and to carry collected ash and discharge the ash at the rear of the stoker, grate sections carried by respective pans and each formed of bars arranged with combustion air spaces therebetween and extending transversely of the direction of movement of the grate, a continuous .guide track for each chain which serves to support the chain and constrain it to move in a predetermined path, each ash pan being formed with a front retaining ledge and a rear retaining wall, each adjacent pair of ash pans being so close to one another in the upper run of the grate that the rear retaining wall of the front ash pan and the front retaining ledge of the rear ash pan form a restricted passageway for combustion air to flow upwardly from the space below the upper run of the grate and through the grate section of the rear ash pan.

3. A stoker as claimed in claim 2, wherein the air space below the upper run of the grate is longitudinally sectionalised, and means are provided for separately controlling the air pressures in different compartments and ash pans in the upper run of the grate provide sealing surfaces co-operating with complementary means in limiting leakage between adjacent air compartments.

4. A stoker as claimed in claim 12, wherein end walls and at least one intermediate wall extending between the iear wall and the transom afford grate bar support suraces.

5. A stoker as claimed in claim 2, wherein the section of grate carried by an ash pan is formed as a unit positioned between opposed part-s of the pan by couplings of the projection and socket type and the section possesses resilience to permit engagement or disengagement of projections and complementary sockets.

6. A stoker as claimed in claim 2, wherein each ash pan is formed at its ends with supporting lugs fitted into complementary recesses in links of respective chains and a lug is locked in the associated recess by a key held in position through engagement with a grate bar or grate bars.

7. A stoker as claimed in claim 6, wherein the key includes a head arranged to fit a recess extension having at its side remote from the lug an opening at least as wide as the recess and at its ends grooves for engagement with the ends of the head from which extends a locating shank arranged to engage grate bars at the edges thereof remote from their fuel supporting surfaces.

8. A stoker as claimed in claim 6, wherein each chain is formed of inner links alternating with outer links and each inner link is formed centrally adjacent its outer edge with a projection extending outwardly with respect to the grate and into which the recess extends and each outer link is formed centrally adjacent its outer edge with a projection extending inwardly with respect to the grate and penetrated by the recess.

9. A stoker as claimed in claim 2, wherein alternate, inner links of the chains are formed at their inner faces with bosses for engagement by the teeth of driving sprocket wheels.

10. A stoker as claimed in claim 2, wherein the links of each chain are hinged together by means of bushes in Which roller spindles are rotatably carried.

11. A stoker as claimed in claim 10, wherein the roller spindles extend co-axially through circular chain driving bosses at the inner faces of the inner links.

12. A stoker as claimed in claim 2, wherein the links of each chain at their outer faces are formed adjacent their outer edges with longitudinal ribs arranged to overlap a fixed longitudinally extending member at a side of the upper run of the grate.

13. A stoker as claimed in claim 2, wherein between the upper and lower runs of the grate is provided a windbox for the discharge of air through the upper run of the grate and the stoker frame comprises side elements joined by transverse elements including plates forming ends of the windbox and dividing the windbox into sections having separate air control dampers.

14. A travelling grate stoker according to claim 2, wherein the front retaining ledge extends upwardly and forwardly to form a front lip and wherein the rear retaining wall extends forwardly and upwardly and terminates in a generally vertical upper end portion.

15. A stoker according to claim 2, wherein the ash pans of each adjacent pair of ash pans are so close to one another in the upper run of the grate that the rear end of the bottom of the front ash pan is to the rear of the front lip of the rear ash pan.

16. A stoker according to claim 2, wherein each ash pan is formed with a front transom supported in spaced relation above the front retaining ledge of the pan so that air flowing upwardly between the ash pan and the adjacent preceding ash pan is free to flow rearwardly into the ash pan beneath the grate section.

17. A stoker according to claim 16, wherein the upper part of the transom has a forwardly and upwardly inclined front surface adapted to overhang the vertical upper end portion of the rear retaining wall of an adjacent preceding ash pan.

18. A stoker according to claim 16, wherein each grate section is formed as a unit comprising grate bars so spaced that combustion air may flow upwardly in the gaps be- 7 8 tween the bars, and wherein the grate section is posi- 1,863,541 6/1932 Luche 11040 tioned between the transom at the front of the ash pan 1 890 210 12/1932 Bennis 11 4 and the upper end portion of the rear retaining wall of 1 904 503 4 /1933 Miller 110 40 the ash pan by couplings of the pro ection and socket type, 3,095,839 7/1963 Vollhardt et al- 110 40 the couplings providing a spacing between the transom 5 and the front grate for the appropriate upward flow of combustion air therebetween and a spacing between the FOREIGN PATENTS rear grate bar and the upper end portion of the rear retaining wall for the appropriate upward fiow of combus- 352522 4/1922 Germany I 908,902 4/1954 Germany.

tion air therebetween.

926,984 4/1955 Germany.

References Cited by the Examiner v UNITED STATES A T KENNETH W. SPRAGUE, Primary Examiner.

970,868 9/1910 Wood 1104O 

1. A TRAVELLING GRATE STOKER COMPRISING A PAIR OF ENDLESS CHAINS DISPOSED SIDE-BY-SIDE IN SPACED RELATIONSHIP, A SERIES OF ASH PANS EXTENDING BETWEEN AND CARRIED BY THE CHAINS AND ADAPTED TO COLLECT ASH FALLING THROUGH SUPERJACENT PARTS OF THE UPPER RUN OF THE GRATE AND TO CARRY THE COLLECTED ASH AND TO DISCHARGE THE ASH AT THE REAR OF THE STOKER, GRATE SECTIONS CARRIED BY RESPECTIVE PANS AND EACH FORMED OF BARS ARRANGED WITH COMBUSTION AIR SPACES THEREBETWEEN AND EXTENDING TRANSVERSELY OF THE DIRECTION OF MOVEMENT OF THE GRATE, A CONTINUOUS GUIDE TRACK FOR EACH CHAIN WHICH SERVES TO SUPPORT THE CHAIN AND CONSTRAIN IT TO MOVE IN A PREDETERMINED PATH, MEANS LONGITUDINALLY SECTIONALIZING THE AIR SPACE BELOW THE UPPER RUN OF THE GRATE INTO COMPARTMENTS, AND MEANS FOR SEPARATELY CONTROLLING THE AIR PRESSURES IN DIFFERENT COMPARTMENTS, SAID ASH PANS IN THE UPPER RUN OF THE GRATE PROVIDING SEALING SURFACES COOPERATING WITH COMPLEMENTARY MEANS IN LIMITING LEAKAGE BETWEEN ADJACENT AIR COMPARTMENTS. 